fix: fix vue add/invoke bug when user does not have yarn installed (#3806)

closes #3804

Author: haoqunjiang

packages/@vue/cli-ui/apollo-server/util/command.js

@@ -10,5 +10,5 @@ exports.getCommand = function (cwd = undefined) {
   if (!cwd) {
     return loadOptions().packageManager || (hasYarn() ? 'yarn' : hasPnpm3OrLater() ? 'pnpm' : 'npm')
   }
-  return hasProjectYarn(cwd) ? 'yarn' : hasProjectPnpm() ? 'pnpm' : 'npm'
+  return hasProjectYarn(cwd) ? 'yarn' : hasProjectPnpm(cwd) ? 'pnpm' : 'npm'
 }

packages/@vue/cli/lib/add.js

@@ -27,7 +27,7 @@ async function add (pluginName, options = {}, context = process.cwd()) {
   log(`📦  Installing ${chalk.cyan(packageName)}...`)
   log()
 
-  const packageManager = loadOptions().packageManager || (hasProjectYarn(context) ? 'yarn' : hasProjectPnpm() ? 'pnpm' : 'npm')
+  const packageManager = loadOptions().packageManager || (hasProjectYarn(context) ? 'yarn' : hasProjectPnpm(context) ? 'pnpm' : 'npm')
   await installPackage(context, packageManager, options.registry, packageName)
 
   log(`${chalk.green('✔')}  Successfully installed plugin: ${chalk.cyan(packageName)}`)

packages/@vue/cli/lib/invoke.js

@@ -145,7 +145,7 @@ async function runGenerator (context, plugin, pkg = getPkg(context)) {
     log(`📦  Installing additional dependencies...`)
     log()
     const packageManager =
-      loadOptions().packageManager || (hasProjectYarn(context) ? 'yarn' : hasProjectPnpm() ? 'pnpm' : 'npm')
+      loadOptions().packageManager || (hasProjectYarn(context) ? 'yarn' : hasProjectPnpm(context) ? 'pnpm' : 'npm')
     await installDeps(context, packageManager, plugin.options && plugin.options.registry)
   }